Hydraulic control for dies in ram type presses



9, 1966 F. M. WWW mmm HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSESFiled June 25, 1963 IN VEN TOR.

HI I I gy h zr/zamm United States Patent M 3,2643% HYDRAULIC CONTROL FDRDIES IN RAM TYPE PRESSES Floyd M. Williamson, Detroit, Mich, assignor toDi-lDro Engineering Company, Detroit, Mich, a corporation of MichiganFiled June 25, 1963, Ser. No. 290,557 7 Claims. (Cl. 72351) Thisinvention relates to a hydraulic control system for die pads in ram typepresses and has particular reference to hydraulic cushions for movabledie pads in presses and hydraulic control means for providing differentresistances to retraction of two or more die pads upon closing of thepress.

The present invention is directed to a hydraulic system for one die orset of dies in a press in which resistance to retraction of the die padis provided by forcing a relatively small quantity of hydraulic fluidthrough a pressure relief valve while the die pad is returned to itsextended position by relatively low pressure hydraulic fluid reactingagainst a larger area of the reciprocable piston which reacts againstthe die. Another die or set of dies react against a second piston whichis reciprocablewithin a cylinder bore within the first piston and isalso connected to the hydraulic fluid source through the pressure reliefvalve upon closing of the press. With this arrangement, it is possibleto select the diameters of the telescoping pistons in such a way as toprovide different predetermined resistances to retraction of the severaldie pads so as to assist in forming operations and return the die padsto their extended positions for stripping the work from the dies. Theinvention, therefore, provides two or more movable die pads controlledby a single pressure relief valve thereby providing economy inmanufacturing costs and a reduction in the size of the control system.

A principal object of the invention is to provide a new and improvedhydraulic control system for dies in ram type presses. Another object ofthe invention is to provide a new and improved hydraulic control systemfor dies which results in substantial saving in manufacturing costs andin the space required for the control system on the press. Anotherobject of the invention is to provide a hydraulic cushion for two ormore dies in which different resistances to the retraction of the diesin provided through a single control valve.

Other and further objects of the invention will be apparent from thefollowing description and claims and may be understood by reference tothe accompanying drawings, of which there is one sheet, which by way ofillustration shows a preferred embodiment of the invention and what Inow consider to be the best mode applying the principles thereof. Otherembodiments of the invention may be used without departing from thescope of the present invention as set forth in the appended claims.

As shown in the drawing, a ram .type mechanical press may include amovable die pad 10 and a movable die pad 12 over which the work is to beformed upon closing of the ram (not shown) of the press. The hydrauliccontrol system for the dies 10 and 1 2 includes a tank 14 containinghydraulic fluid under a regulated pressure of, for example, 100 poundsper square inch. A cylinder block 16 is provided with a cylinder bore 18within which a piston 20 is reciprocable. The piston 20 carries a washer22 which sealingly engages the cylinder bore 18. A second piston 24 isintegral with the piston 21 but is of smaller diameter and carries awasher 26 which sealingly engages a cylinder bore 28 in the cylinderblock 16. The piston 20 is provided with a cylinder bore 30 containing areciprocable piston 32 which is provided at its lower Patented August 9,1966 ICC end with a washer 34 sealingly engaging the cylinder bore 30. Apassage 36 in the piston 24 provides communication between the lower endof the cylinder bore and the cylinder bore 28.

The piston 20 is provided at its upper end with a reduced diameterportion defining a shoulder 40 for supporting a series of rods 42 whichare engaged by the movable die pad 10. The lower ends of the rods 42 aresecured to a pair of support rings 44, one of which is seated on theshoulder 40 and the other of which is engaged by a retaining Washer 46to rigidly mount the rods 42 on the upper end of the piston 20. A seriesof rods 43 are mounted in a similar manner on the upper end of thepiston 32 and engage the movable die pad .12.

A hydraulic fluid connection 50 leads from the lower end of tank 14 to afitting 52 on the cylinder block 16. A passage 54 provides communicationbetween the lower end of cylinder 18 and the hydraulic line 50. Ahydraulic fluid line 56 also leads from the tank 14 to a valve unit 58which includes a pressure relief valve 60 and a ball check valve 62.Cylinder block '16 is provided with a passage 64 providing communicationbetween the lower end of the cylinder 28 and a line as communicatingwith the interior of the valve unit 58.

When the press is opened, hydraulic fluid under pressure in the tank 14will be forced through line 50 and passage 54 into the lower end of thecylinder 18 to react against the underside of the piston 28. Thehydraulic fluid under tank pressure will also flow through line 56 intopassage 68 in the valve 58 past check valve 62 and through passage 70,line 66, and passage 64 into the lower end of the cylinder 28 to reactagainst the underside of the piston 24 and through passage 36 into thelower end of the cylinder 30 to react against the underside of thepiston 32. The pistons 20, 24 and 32 will thus all be forced upwardly byhydraulic fluid under tank pressure to move the die pads 1d and 12 totheir extended positions shown in the drawing.

When the press closes, hydraulic fluid in the cylinder 30 and thecylinder 28 is trapped by the check valve '62 and then returned to thetank 14 only by forcing open the pressure relief valve 60 which may beset by an adjusting screw 72 to open .at a predetermined pressure. Thehydraulic fluid in the cylinder 18 is returned directly to the tank 14through passage 54 and the connection 50. The pistons 24 and 32 are:both subjected to the same pressures which resist retraction of thepistons and retraction of both pistons 24 and 32 is controlled by thesingle pressure relief valve 611. However, by selecting differentdiameters for the pistons 24 and 32, or different areas exposed to thepressure fluid resisting their retraction, different predeterminedresistances to movement of the die pads is provided. The differences inthe areas of the pistons may also be utilized to assist in stripping thework from the dies.

The control system described not only has the advantage of providing forcontrol of two or more sets of dies through a single control valve butalso provides a relatively large area reacted upon by hydraulic fluidunder tank pressure to return the dies to their extended positions whileonly a relatively small area reacts against the high pressure fluidwhich is trapped by the pressure relief valve upon closing of the press.This latter feature is disclosed in my co-pending application Serial No.114,264, filed June 1, 1961, for Hydraulic Control for Die Pads inPresses, now U.S. Patent No. 3,124,340 and in my co-pending applicationSerial No. 145,297, filed October 16, 196 1, [for Hydraulic Control lforDies in Ram Type Presses, the present application being a continuationin part of such prior co-pending applications.

While I have illustrated and described a preferred embodiment of myinvention, it is understood that this is capable of modification, and Itherefore do not wish to be limited to the precise details set forth butdesire to avail myself of such changes and alterations as fall withinthe purview of the following claims.

I claim:

1. In a press having a pair of dies each movable from an extended to aretracted position upon closing of the press, a hydraulic cushionreacting on said dies so as to resist retraction thereof, said hydrauliccushion comprising a tank of hydraulic fluid under pressure, a cylinderhaving two bores, a piston reciprocable in each bore and reacting on oneof said dies so as to be retracted as said one die moves toward itsretracted position, a hydraulic circuit including fluid flow connectionsbetween said tank and said cylinder bores through which hydraulic fluidunder tank pressure is supplied to each cylinder bore when the pressopens so as to cause said pistons to bias said one die toward itsextended position, said fluid flow connections providing for hydraulicfluid flow from said cylinder bores toward said tank upon the retractionof said pistons, a pressure relief valve in the connection between oneof said bores and said tank so as to provide a resistance substantiallygreater than tank pressure to the retraction of the piston in said onebore, said pistons being integral and being provided with a cylinderbore communicating with said one cylinder bore, a third pistonin saidcylinder bore in said pistons, the other of said dies being arranged toreact on said third piston to provide a resistance substantially greaterthan tank pressure to the retraction of said third piston in itscylinder bore, said pistons having different diameters so as to providedifferent predetermined resistances to retraction of said dies uponclosing of the press.

2. In a press having a pair of dies each movable from an extended to aretracted position upon closing of the press, a hydraulic cushionreacting on said dies so as to resist retraction thereof, said hydrauliccushion comprising a tank of hydraulic fluid under pressure, a cylinderhaving two bores, a piston reciprocable in each bore and reacting on oneof said dies so as to be retracted as said one die moves toward itsretracted position, a hydraulic circuit including fluid flow connectionsbetween said tank and said cylinder bores through which hydraulic fluidunder tank pressure is supplied to each cylinder bore when the pressopens so as to cause said pistons to bias said one die toward itsextended position, said fluid flow connections providing for hydraulicfluid flow from said cylinder bores toward said tank upon the retractionof said pistons, a pressure relief valve in the connection between oneof said bores and said tank so as to provide a resistance substantiallygreater than tank pressure to the retraction of the piston in said onebore, said pistons being integral and being provided with a cylinderbore communicating with said one cylinder bore, a third piston in saidcylinder bore in said pistons, the other of said dies being arranged toreact on said third piston to provide a resistance substantially greaterthan tank pressure to the retraction of said third piston in itscylinder bore, the piston in said one bore and said third piston havingdifferent areas exposed to the hydraulic fluid in their respectivecylinder bores so as to provide different predetermined resistances toretraction of said dies upon closing of the press.

3. In a press having a pair of dies each movable from an extended to aretracted position upon closing of the press, a hydraulic cushionreacting on said dies so as to resist retraction thereof, said hydrauliccushion comprising a tank of hydraulic fluid under pressure, a cylinder,a piston reciprocable in said cylinder and reacting on one of said diesso as to be retracted as said one die moves toward its retractedposition, a hydraulic circuit including fluid flow connections betweensaid tank and said cylinder through which hydraulic fluid under tankpressure is supplied to said cylinder when the press opens 80 as tocause said piston to bias said one die toward its extended position,said fluid flow connections providing for hydraulic fluid flow from saidcylinder toward said tank upon the retraction of said piston, a pressurerelief valve in the connection between said cylinder and said tank so asto provide a resistance substantially greater than tank pressure to theretraction of said piston, said piston being provided with a cylinderbore communicating with said cylinder, a second piston in said cylinderbore, the other of said dies being arranged to react on said secondpiston to provide a resistance substantially greater than tank pressureto the retraction of said second piston in its cylinder bore, saidpistons having different areas exposed to the hydraulic fluid in theirrespective cylinder bores so as to provide different predeterminedresistances to retraction of said dies upon closing of the press.

4. In a press according to claim 3, a third cylinder having a pistontherein reacting against one of said dies and a fluid flow connectionbetween said tank and said third cylinder through which hydraulic fluidunder tank pressure is supplied to said third cylinder when the pressopens to assist in biasing said one die toward its extended position,

5. In a press according to claim 4, said piston in said third cylinderand said first mentioned piston being integral.

6. In a press having a pair of dies each movable from an extended to aretracted position upon closing of the press, a hydraulic cushionreacting on said dies so as to resist retraction thereof, said hydrauliccushion comprising a tank of hydraulic fluid under pressure, a cylinder,a piston reciprocable in said cylinder bore and reacting on one of saiddies so as to be retracted as said one die moves toward its retractedposition, said piston having a cylinder bore therein, a second piston insaid last mentioned cylinder bore and reacting on the other of said diesso as to be retracted as said other die moves to its retracted position,a hydraulic circuit including fluid flow connections between said tankand said cylinder bores through which hydraulic fluid under tankpressure is supplied to each cylinder bore when the press opens so as tocause said pistons to bias said dies toward their extended positions,said fluid flow connections providing for hydraulic fluid flow from saidcylinder bores toward said tank upon the retraction of said pistons, apressure relief valve in the connections between said bores and saidtank so as to provide a resistance subtantially greater than tankpressure to the retraction of said pistons, said pistons havingdifferent areas exposed to the hydraulic fluid in their respectivecylinder bores so as to provide different predetermined resistances toretraction of said dies upon closing of the press.

7. In a press having a pair of dies each movable from an extended to aretracted position upon closing of the press, a hydraulic cushionreacting on said dies so as to resist retraction thereof, said hydrauliccushion comprising a tank of hydraulic fluid under pressure, a cylinderbore, a piston reciprocable in said cylinder bore and reacting on one ofsaid dies so as to be retracted as said one die moves toward itsretracted position, said piston having a cylinder bore therein, a secondpiston reciprocable in said last-mentioned cylinder bore and reacting onthe other of said dies so as to [be retracted as said other die moves toits retracted position, a hydraulic circuit including fluid flowconnections between said tank and said cylinder bores through whichhydraulic fluid under tank pressure is supplied to each cylinder borewhen the press opens so as to cause said pistons to bias said diestoward their extended positions, said fluid flow connections providingfor hydraulic fluid flow from said cylinder bores toward said tank uponthe retraction of said pistons, a pressure relief valve in theconnection between one of said bores and said tank so as to provide aresistance substantially greater than tank pressure to the retraction ofthe piston in said one bore,

different areas exposed to the hydraulic fluid in their 5 respectivecylinder bores so as to provide difierent predetermined resistances toretraction of said dies upon closing of the press.

References Cited by the Examiner UNITED STATES PATENTS Hothersall 72351Gaudreau 72351 Williamson 267-1 Williamson 2671 CHARLES W. LANHAM,Primary Examiner. R. J. HERBST, Assistant Examiner.

1. IN A PRESS HAVING A PAIR OF DIES EACH MOVABLE FROM AN EXTENDED TO ARETRACTED POSITION UPON CLOSING OF THE PRESS, A HYDRAULIC CUSHIONREACTING ON SAID DIES SO AS TO RESIST RETRACTION THEREOF, SAID HYDRAULICCUSHION COMPRISING A TANK OF HYDRAULIC FLUID UNDER PRESSURE, A CYLINDERHAVING TWO BORES, A PISTON RECIPROCABLE IN EACH BORE AND REACTING ON ONEOF SAID DIES SO AS TO BE RETRACTED AS SAID ONE DIE MOVES TOWARD ITSRETRACTED POSITION, A HYDRAULIC CIRCUIT INCLUDING FLUID FLOW CONNECTIONSBETWEEN SAID TANK AND SAID CYLINDER BORES THROUGH WHICH HYDRAULIC FLUIDUNDER TANK PRESSURE IS SUPPLIED TO EACH CYLINDER BORE WHEN THE PRESSOPENS SO AS TO CAUSE SAID PISTONS TO BIAS SAID ONE DIE TOWARD ITSEXTENDED POSITION, SAID FLUID FLOW CONNECTIONS PROVIDING FOR HYDRAULICFLUID FLOW FROM SAID CYLINDER BORES TOWARD SAID TANK UPON THE RETRACTIONOF SAID PISTONS, A PRESSURE RELIEF VALVE IN THE CONNECTION BETWEEN ONEOF SAID BORES AND SAID TANK SO AS TO PROVIDE A RESISTANCE SUBSTANTIALLYGREATER THAN TANK PRESSURE TO THE RETRACTION OF THE PISTON IN SAID ONEBORE, SAID PISTONS BEING INTEGRAL AND BEING PROVIDED WITH A CYLINDERBORE COMMUNICATING WITH SAID ONE CYLINDER BORE, A THIRD PISTON IN SAIDCYLINDER BORE IN SAID PISTONS, THE OTHER OF SAID DIES BEING ARRANGED TOREACT ON SAID THIRD PISTON TO PROVIDE A RESISTANCE SUBSTANTIALLY GREATERTHAN TANK PRESSURE TO THE RETRACTION OF SAID THIRD PISTON IN ITSCYLINDER BORE, SAID PISTONS HAVING DIFFERENT DIAMETERS SO AS TO PROVIDEDIFFERENT PREDETERMINED RESISTANCES TO RETRACTION OF SAID DIES UPONCLOSING OF THE PRESS.